The Investigation of Developing Flow and Heat Transfer in a Long Converging Duct

The hydrodynamic and thermal development of turbulent boundary layers subjected to streamwise acceleration has been investigated. This was accomplished by obtaining detailed flow and temperature measurements over 52 entrance heights of a converging channel (with one wall heated) and with uniform velocity and temperature profiles at entry. Results are presented for three Reynolds numbers of 4000, 16,000, and 21,000 corresponding to acceleration parameter k levels of 2.31×10⁻⁶, 5.78×10⁻⁷, and 4.47×10⁻⁷, respectively. At acceleration parameter levels of 2.3×10⁻⁶ the flow behaves in a laminarlike fashion in all respects. Even at an acceleration parameter level of 4.5×10⁻⁷ the skin friction coefficients and Stanton number values are well below those encountered in parallel channel flow at corresponding Reynolds numbers. The entry region behavior is further complicated by the combined effects of thin inlet boundary layers and streamwise acceleration. These entry effects are perhaps more obvious in the Stanton number development. The well-defined entry conditions make these detailed measurements suitable for turbulence model validation and refinement.